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Effects of ion irradiation on microstructure and properties of zirconium alloysdA review
Chunguang Yan,Rongshan Wang,Yanli Wang,Xitao Wang,Guanghai Bai 한국원자력학회 2015 Nuclear Engineering and Technology Vol.47 No.3
Zirconium alloys are widely used in nuclear reactors as structural materials. During the operation, they are exposed to fast neutrons. Ion irradiation is used to simulate the damage introduced by neutron irradiation. In this article, we briefly review the neutron irradiation damage of zirconium alloys, then summarize the effect of ion irradiation on microstructural evolution, mechanical and corrosion properties, and their relationships. The microstructure components consist of dislocation loops, second phase precipitates, and gas bubbles. The microstructure parameters are also included such as domain size and microstrain determined by X-ray diffraction and the S-parameter determined by positron annihilation. Understanding the relationships of microstructure and properties is necessary for developing new advanced materials with higher irradiation tolerance.
Investigation of the Voltage Collapse Mechanism in Three-Phase PWM Rectifiers
Chunguang Ren,Huipeng Li,Yu Yang,Xiaoqing Han,Peng Wang 전력전자학회 2017 JOURNAL OF POWER ELECTRONICS Vol.17 No.5
Three-phase pulse width modulation (PWM) rectifiers are usually designed under the assumption of ideal ac power supply and input inductance. However, non-ideal circuit parameters may lead to a voltage collapse of PWM rectifiers. This paper investigates the mechanism of voltage collapse in three-phase PWM rectifiers. An analytical stability boundary expression is derived by analyzing the equilibrium point of the averaging state space model, which can not only accurately locate the voltage collapse boundary in the circuit parameter domain, but also reveal the essential characteristic of the voltage collapse. Results are obtained and compared with those of the trial-error method and the Jacobian method. Based on the analysis results, the system parameters can be divided into two categories. One of these categories affects the critical point, and other affects only the instability process. Furthermore, an effective control strategy is proposed to prevent a vulnerable system from being driven into the instability region. The analysis results are verified by the experiments.
박춘광(Chunguang Piao),김진오(Jin Oh Kim) 한국소음진동공학회 2015 한국소음진동공학회 학술대회논문집 Vol.2015 No.10
This paper theoretically deals with vibration characteristics of a transducer coupled with a piezoelectric disc. Natural frequencies of in-plane and out-of-plane modes of the transducer were obtained from the equations of motion and boundary conditions by theoretical analysis. Moreover, the natural frequencies were obtained from the impedance curves calculated by the finite-element analysis also. The theoretical analysis was verified by comparing the two analysis results. The radial in-plane and axial out-of-plane vibrations appear coupled in the axisymmetric vibration modes. Out-of-plane vibration modes of the piezoelectric transducer were much affected due to the coupled disc, but in-plane vibration modes were not.
박춘광(Chunguang Piao),김진오(Jin Oh Kim) 한국소음진동공학회 2015 한국소음진동공학회 학술대회논문집 Vol.2015 No.4
This paper deals with the vibration characteristics of the piezoelectric disc laminated with an elastic disc. Natural frequencies of the laminate layers were obtained by theoretical analysis, and they were compared with the finite-element analysis and experiment. The radial in-plane vibration and axial out-of-plane vibration appear coupled in axisymmetric vibration modes. Due to the elastic disc, out-of-plane vibration modes of the piezoelectric disc were much affected, but in-plane vibration modes were not.